Some roles need to be recast
Let's face it. Some members of the cast are just too old now. Famke Jansson, Hugh Jackman, Alan Cumming and Halle Berry have all had good runs but they've gotten a bit too old for their current roles.
Let's hear it for some recasting suggestions
I personally would go with
Rose Leslie - Phoenix
Wolverine - Emile Hirsch
Nightcrawler - Daniel Brühl
Storm - Jennifer Hudson
And if something happens to Patrick Stuart or Ian McKellan, I'd have Christoph Waltz play old Magneto and old Xavier would be portrayed by Ben Kingsley.